Want proof markets are often more unpredictable than your daily Sweetgreen order (curried cauliflower or broccoli? Or Harvest Bowl? It's hard)?

The Dow was down 600 points Thursday with 90 minutes of market open-ness to go — then it inexplicably rose 850 to finish up over 1%. That's its biggest same-day rebound since 2010. Robot traders are fist bumping.

1. Blue Apron's biggest partnership ever = Biggest day ever

Rollin' up to the buffet with a suitcase... Shares of Blue Apron surged7% for their best day in ever. Sadly, the stock's still worth less than a McD's Dollar Menu (about 90 cents) and fallen 77% in 2018. But Thursday's binge was the result of a new partnership with WW -- the slim fit artist formerly known as Weight Watchers.

They're on a let-me-cook-to-impress-you dinner date... Blue Apron's whipping up some ingredient-controlled, calorie-limited meal kits exclusively for WW. So WW gets to give its customers a convenient new feature -- And Blue Apron gets access to a major customer base it's desperate for. FYI, WW hates the word "diet."

The Takeaway: "Differentiation" is the key ingredient... Amazon, Kroger, and even Nestlé now sell meal kits. Your roommate who loves garlic is launching one. That fresh competition's caused Blue Apron's number of subscriptions to fall by 1/3 to 646K. Creating new lines, like aggressively veggie WW "health kits," is the new growth recipe.

2. McDonald's All-day McMuffin is hurting breakfast sales

Protein, protein, and protein, please… Americans love McDonald’s meat, egg, and cheese sandwiches so much it hurts (pancake bread optional). Breakfast fills up about a quarter of McD's sales -- And according to WSJ, Micky D’s breakfast is facing competition from the rest of your day.

All-Day Breakfast ruined breakfast… Historically diners literally set their alarms for McMuffins. Restaurant owners (aka Franchisees) say the ol' 10:30AM breakfast cutoff got people through its Golden Arches early. Now that breakfast's all day, diners skip “breakfast” to get breakfast at lunch or dinner instead.

The Takeaway: Sometimes "give the customer what they want" hurts... Franchisees said not to mess with breakfast because it’s their most profitable meal of the day (faux egg ingredients are cheap). But the team over in corporate disagreed, offering up 24-hour on-call McMuffins. The people are happy. Profits aren’t.